Photophysical properties of lumichromes in water

Sikorski, Marek; Sikorska, Ewa; Koziołowa, Anna; Moreno, R Gonzalez; Bourdelande, J. L.; Steer, Ronald P.; Wilkinson, Frances

doi:10.1016/s1011-1344(01)00134-8

Cited by 76 publications

(65 citation statements)

References 29 publications

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“…Instead, LCR is known as a toxic substance, transferring light energy to substrates (photosensitization type 1) and oxygen (photosensitization type 2), creating reactive compounds like singlet state oxygen (35). Accordingly, we found a sharp decrease of cell density when H. salinarum was grown in the light and in the presence of 40 M LCR.…”

Section: Working Mode 2 Directed Degradation Of Excited Rf-when Incomentioning

confidence: 64%

Dodecin Is the Key Player in Flavin Homeostasis of Archaea

Grininger

Staudt

Johansson

et al. 2009

Journal of Biological Chemistry

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Flavins are employed to transform physical input into biological output signals. In this function, flavins catalyze a variety of light-induced reactions and redox processes. However, nature also provides flavoproteins with the ability to uncouple the mediation of signals. Such proteins are the riboflavin-binding proteins (RfBPs) with their function to store riboflavin for fast delivery of FMN and FAD. Here we present in vitro and in vivo data showing that the recently discovered archaeal dodecin is an RfBP, and we reveal that riboflavin storage is not restricted to eukaryotes. However, the function of the prokaryotic RfBP dodecin seems to be adapted to the requirement of a monocellular organism. While in eukaryotes RfBPs are involved in trafficking riboflavin, and dodecin is responsible for the flavin homeostasis of the cell. Although only 68 amino acids in length, dodecin is of high functional versatility in neutralizing riboflavin to protect the cellular environment from uncontrolled flavin reactivity. Besides the predominant ultrafast quenching of excited states, dodecin prevents light-induced riboflavin reactivity by the selective degradation of riboflavin to lumichrome. Coordinated with the high affinity for lumichrome, the directed degradation reaction is neutral to the cellular environment and provides an alternative pathway for suppressing uncontrolled riboflavin reactivity. Intriguingly, the different structural and functional properties of a homologous bacterial dodecin suggest that dodecin has different roles in different kingdoms of life.Flavins are a major class of cofactors that are able to accept and donate electrons as well as to absorb visible light. Flavins consist of a nonconserved aliphatic moiety, covalently linked to a conserved aromatic isoalloxazine ring ( In all flavins, the catalytically active unit is the isoalloxazine substructure (2-4). To handle the reactivity of the isoalloxazine ring, FMN and FAD are tightly bound to flavoenzymes. Finely tuned binding restricts the reaction spectrum of FMN and FAD to discrete, beneficial reaction pathways, preventing harmful side reactions. Reported functions of flavoenzymes include transferring electrons from and to reactive centers (e.g. respiratory chain) as well as employing light for the induction of radical reactions (e.g. DNA-photolyase) or conformational changes (e.g. phototropin) (5-8). In the biosynthesis, the full catalytic power of flavins has already formed at the stage of the FMN and FAD precursor RF (see Fig. 1). As RF is not used as an enzymatically active compound, it is, different to FMN and FAD, not integrated into flavoenzymes. To avoid a negative impact of uncontrolled flavin reactivity by free RF, nature established sequestering devices termed riboflavin-binding proteins (RfBPs). These proteins have been shown to store and distribute RF in eukaryotes, ensuring a fast supply of FMN and FAD (9, 10).The small flavoprotein dodecin from the archaeon Halobacterium salinarum was reported to bind RF with high affinity and to extensiv...

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Section: Working Mode 2 Directed Degradation Of Excited Rf-when Incomentioning

confidence: 64%

Dodecin Is the Key Player in Flavin Homeostasis of Archaea

Grininger

Staudt

Johansson

et al. 2009

Journal of Biological Chemistry

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“…and Sikorska et al . that have reported the first two band maxima for lumiflavin in water at λ 1 = 445 nm (2.79 eV) and λ 2 = 367 nm (3.38 eV) . In this section, we want to address to the solvent effect on the few low‐lying excited states that are needed to understand the experimental spectrum .…”

Section: Resultsmentioning

confidence: 99%

Spectroscopic Properties of Lumiflavin: A Quantum Chemical Study

Kar

Borin

Ding

et al. 2018

Photochem & Photobiology

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In this work, the electronic structure and spectroscopic properties of lumiflavin are calculated using various quantum chemical methods. The excitation energies for ten singlet and triplet states as well as the analysis of the electron density difference are assessed using various wave function‐based methods and density functionals. The relative order of singlet and triplet excited states is established on the basis of the coupled cluster method CC2. We find that at least seven singlet excited states are required to assign all peaks in the UV/Vis spectrum. In addition, we have studied the solvatochromic effect on the excitation energies and found differential effects except for the first bright excited state. Vibrational frequencies as well as IR, Raman and resonance Raman intensities are simulated and compared to their experimental counterparts. We have assigned peaks, assessed the effect of anharmonicity, and confirmed the previous assignments in case of the most intense transitions. Finally, we have studied the NMR shieldings and established the effect of the solvent polarity. The present study provides data for lumiflavin in the gas phase and in implicit solvent model that can be used as a reference for the protein‐embedded flavin simulations and assignment of experimental spectra.

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“…The main interest of the biochemical community in lumichrome so far was focused on the appearance as a photosensitizer. [44][45][46] The primarily non-toxic lumichrome was thereby identified to be efficient in transferring excitation energy to substrates (photosensitization type 1) and oxygen (photosensitization type 2) and thus exerting a "secondary toxic" effect.…”

Section: Biological Implicationsmentioning

confidence: 99%